Manufacture of rubber articles containing cotton fabric



Patented June 30, 1936 UNITED STATES PAT'ET OFFICE MANUFACTURE OF RUBBER ARTICLES CONTADIING COTTON FABRIC No Drawing. Application October 13, 1934, Serial No. 748,217

6 Claims. (Cl. 91-68) This invention relates to the manufacture of rubber products containing braided or woven cotton fabric.

When products of this character are exposed to moisture and the usual atmospheric conditions, the cotton is subject to mildew or other fungus growth thereby weakening and destroying the usefulness of the product. Fire hose, belting and cable covering containing rubber and cotton are particularly subject to this type of destruction because of their use in the presence of water and dampness. It is desirable, therefore, that the cotton be subjected to a treatment which will prevent or retard the growth of mildew.

Some of the well known methods for rendering materials generally resistant to attack by mildew include the use of copper salts, creosotes, creosote-type materials, phenols, mercury salts, etc.

29 These commonly employed processes cannot be used in the manufacture of rubber products for the following reasons.

I Copper salts have a deleterious effect on rubher, even when used in relatively small per- 25 centages. The same is true of creosotes and creosote-type materials. In addition, creosotes and creosote-type materials are volatile at atmospheric temperature, and therefore are not permanent when exposed to weathering conditions. 30 Phenols are too volatile to withstand the heat of vulcanization of the rubber. Mercury salts are hazardous to human life.

Some of the requisites of a treatment to prevent mildew growth on cotton used in the fabri- 35 cation of rubber products are as follows:

(1) The treatment must be permanent when exposed to weathering conditions.

' (2) The treatment shall be of such a nature as not to have a deleterious effect on rubber.

(3) It must be stable enough in character that it will not be broken up by the heat of vulcanization in the presence of sulphur.

(4) The material used for the mildew treat- 45 ment must be soluble in some solution, preferably water, in order that it may thoroughly wet and impregnate the cotton.

(5) The solution must be of a character that it will not be necessary to use a mangle or other 50 forcible means for impregnating the fabric because, if such means is used, the fabric is likely to be injured during the impregnating.

(6) After the fabric has been thoroughly impregnated with the treatment it must then be 55 converted from the water soluble form to a water insoluble material in order that it may not be washed out during use.

(7) This insoluble material must be deposited in the cotton in an amorphous or colloidal form or so finely crystalline that it will not injure the 5 fabric during the handling it will receive in service. l

(8) The insoluble material must be of such a character that it will not diminish materially the strength of the fabric. v 10 (9) It must be deposited in such a manner as to make a substantially continuous surface over the fibre so that mildew cannot form between the adjacent particles of the inhibiting material.

(10) It must not substantially impair the fiexi- 15 bility of the finished fabric.

After a careful study of the materials ordinarily used to prevent the growth of mildew, it seemed that the well known treatment of fabrics with rare earth salts was the only treatment that would meet the requirements outlined above. The most commonly employed method of this general practice is to impregnate fabrics with water solutions of the chlorides of the rare earth salts and treat with caustic solutions to precipitate the rare earth salts as the insoluble oxides or hydroxides.

If extreme care is exercised throughout the entire process this method is satisfactory, but unless such great care is used during the process of impregnating and drying, the chlorides will be hydrolyzed, producing hydrochloric acid, which in turn readily attacks the cotton, thereby weakening or destroying it. Obviously, if the acetate is used this difllculty would be eliminated and the use of these acetates has been recorded in the literature on this subject. However, repeated efforts to use the acetates resulted in failure due to the fact that the acetate solutions did not properly and uniformly impregnate the fabrics.

The rare earth salts are found in nature as the phosphates and it is only with extreme difflculty that the rare earth acetates can be made commercially free from the phosphates and most commercial acetates contain very material percentages of the phosphates.

I have found that the presence of even such small percentages of the rare earth phosphates as from one-tenth to one-half of 1% prevents the proper impregnation of the rare earth acetate into the relatively heavy cords or yarns used to produce fire hose jackets, belting, cable coverings and the like. Therefore, it is essential that the rare earth acetate be practically free from any contamination of rare earth phosphate.

Thus, I have invented a method of mildew proofing braided or woven fabrics employed in rubber and cotton products by impregnation with a rare earth acetate, and at the same time I have been able to take advantage of the well known mildew-proofing properties of the rare earth salts without the hazards of using the rare earth chlorides. It has been found desirable and sometimes necessary to weave or braid untreated or natural cotton yarns containing natural waxes to provide sufficient lubrication to pass the yarn through the small dies in the heddles of the loom. If these natural waxes are removed, mechanical difficulties of weaving with uniform tension are greatly increased due to friction, as will be well understood by those skilled in the art. 7

I have found that if woven or braided fabrics containing their natural waxes are treated with a water solution of the acetates of the rare earth metal salts substantially free from phosphates, such as lanthanum, neodymium, prazeodymium, ceriumor the like, at a temperature between about 180 F. and 210 F., the fabric will be readily impregnated by this solution. In this range of temperature, the normal-resistance to impregnation due to the natural waxes is overcome. If temperatures lower than about 180 F., are used, with an aqueous solution of the rare earth acetate, inadequate impregnation will result. If temperatures in excess of substantially 210 F., are used, the rare earth acetate will hydrolyze so rapidly that the rare earth acetate will be deposited on the surface of the yarns or fabrics as a powder and will not thoroughly impregnate. Of course, this range of temperatures can be raised if impregnation takes place under pressure.

After the fabric has been thoroughly impregnated, it is dried and immersed in sodium hydroxide solution thereby converting the rare earth acetate into an oxide or hydroxide. It has been found that if the temperatures have been controlled as hereinbefore described, and if the fabric has been thoroughly dried before treating with caustic soda, the fabric will be thoroughly impregnated with the rare earth oxide or hydroxide in an amorphous or extremely fine grain crystal form which adheres very firmly to the fibres, will not powder off, does not impair the strength of the fabric, does not materially impair the flexing of the finished fabric and does very effectively prevent mildew or other fungus growth.

It is to be understood that the invention is not to be limited solely to the use of acetates, since any of the salts of the rare earth metals which are precipitated as hydroxides in the presence of acetic ions may be used. Instead of precipitating a hydroxide by using a caustic, the rare earth metals may be precipitated as phosphates by the use of such materials as sodium phosphate or the like.

The following is an example of the procedure which is being followed in commercially carryme out my invention. Fire hose jackets are soaked for about an hour in a bath of rare earth acetate solution substantially free from phosphates maintained at a concentration of about 6.5 B. at 205 F. The rare earth acetate consists of about 10 to 20% cerium acetate and to of other rare earth acetates. After soaking, the surplus acetate solution is removed. The jackets are then thoroughly dried either at room temperature or at an elevated temperature of about F. The dry jackets containing the rare earth salts are then treated with a caustic solution to precipitate the rare earth salts in the insoluble form.

. After the woven or braided hose jackets are thusthoroughly impregnated with the rare earth salts, they are processed with rubber in the same way as they would be if they were not treated with the rare earth salts.

The same general process is being used by me in the successful mildew-proofing of belting, cable coverings and other fabrics processed with rubber which are used under conditions which promote mildew or other fungus growth.

In some materials such as fire hose, where the cotton is exposed to an unusual amount of water and moisture, it is often found desirable to increase the water resistance of these cotton braids or fabrics by further impregnating with a wax solution.

By the expression substantially free from phosphates I mean less than 1% of phosphates by weight relative to the rare earth acetate or salts.

By the expression rubber I intend to include rubber-like materials such as chloroprene, olefin polysulphides and the like, having a flexibility and elasticity similar to rubber.

I claim as my invention:

1. In the manufacture of rubber products containing woven or braided cotton fabric subject to mildew or other fungus growth wherein cotton yarns are woven or braided into a fabric and thereafter processed with rubber, the improvement which comprises saturating said fabric, prior to processing with rubber, in a solution comprising a rare earth acetate substantially free from rare earth phosphates at a temperature between about 180 F. and 210 F., drying said fabric, treating the dried fabric with a caustic solution to precipitate the rare earth acetate in water insoluble form and to render said fabric resistant to attack by mildew, and thereafter processing said mildew-proofed fabric with rubber to form the desired rubber product.

2. In the manufacture of rubber products containing woven or braided cotton fabric subject to mildew or other fungus growth wherein untreated or natural cotton yarns containing natural waxes are woven or braided into a fabric and thereafter processed with rubber, the improvement which comprises saturating said fabric, prior to processing with rubber, in a solution comprising a rare earth acetate substantially free from rare earth phosphates at a temperature between about 180 F. and 210 F., drying said fabric, treating the dried fabric with a caustic solution to precipitate the rare earth acetate in water insoluble form and to render said fabric resistant to attack by mildew, and thereafter processing said mildew-proofed fabric with rubber to form the desired rubber product.

3. In the manufacture of rubber products containing woven or braided cotton fabric subject to mildew or other fungus growth wherein cotton yarns are woven or braided into a fabric and thereafter processed with rubber, the improvement which comprises saturating said fabric, prior to processing with rubber, in a solution comprising a rare earth acetate substantially free from rare earth phosphates at a temperature between about 180 F. and 210 F., removing the excess solution from said fabric and drying said fabric, treating the dried fabric with a caustic solution to precipitate the rare earth acetate in water insoluble form and to render said fabric resistant to attack by mildew, washing the fabric to remove excess alkali, drying the fabric, and thereafter processing said mildew-proofed fabric with rubber to form the desired rubber product.

4. In the manufacture of rubber products containing woven or braided cotton fabric subject to mildew or other fungus growth wherein cotton yarns are woven or braided into a fabric and thereafter processed with rubber, the improvement which comprises saturating said fabric, prior to processing with rubber, in a solution comprising a salt of a rare earth metal substantially free from rare earth phosphates at a temperature between about 180 F. and 210 F., drying said fabric, treating the dried fabric with a caustic solution to precipitate the salt of the rare earth metal as a water-insoluble hydroxide in the presence of acetic ions and to render said fabric resistant to attack by mildew, and thereafter processing said mildew-proofed fabric with rubber to form the desired rubber product.

5. In the manufacture of rubber products containing woven or braided cotton fabric subject to mildew or other fungus growth wherein cotton yarns are woven or braided into a fabric and thereafter processed with rubber, the improvement which comprises saturating said fabric, prior to processing with rubber, in a solution comprising a salt of a rare earth metal substantially free from rare earth phosphates at a temperature between about 180? F. and 210 F., drying said fabric, treating the dried fabric with a caustic solution to precipitate the salt of the rare earth metal as a water-insoluble hydroxide in the presence of acetic ions, and to render said fabric resistant to attack by mildew, impregnating the treated fabric with wax to increase the water resistance thereof, and thereafter process- I ing said mildew-proofed fabric with rubber to between about 180 F. and 210 F., drying said 20 fabric, treating the dried fabric with a phosphate solution to precipitate the rare earth acetate in water insoluble form as a phosphate and to render said fabric resistant to attack by mildew, and thereafter processing said mildew- 8i proofed fabric with rubber to form the desired rubber product.

CLARENCE 3. WHITE. 

